As sulfonated aromatic compounds are widely used in industry, they have frequently been detected in aquatic environments. This study evaluated the degradation and mineralization of 2,6-naphthalenedisulfonic acid disodium salt (2,6-NS), sodium 2-naphthalenesulfonate (2-NS), benzenesulfonic acid sodium salt (BS), and 4-vinylbenzene sulfonate sodium (4-VBS) by exposing aqueous solutions of these compounds to Co60 irradiation. The radiolytic degradation of these pollutants was found to follow pseudo-first-order kinetics. The dose required to achieve 90% degradation (D90) of these four sulfonated compounds was 0.480 (2,6-NS), 0.390 (2-NS), 0.194 (BS), and 0.280 kGy (4-VBS). The chemical radiolytic yield (Gvalue) decreased as the absorbed dose increased; moreover, the chemical structures of these compounds affected their radiolytic efficacy. No significant reduction in radiolytic degradation was observed in the presence of inorganic anions (SO42-, Cl-). The radiolytic degradation efficiency was higher when hydrogen peroxide (H2O2, a hydroxyl radical (OH) promoter) was added. The results also showed that combining H2O2, persulfate anions (S2O82-, a sulfate radical anion (SO4-) promoter), or N2O gas (a OH radical promoter) with the sulfonated compounds enhanced the radiolytic mineralization yield and process by reducing the required irradiation energy. In terms of the Co60/O2 system, at an absorbed dose of 12 kGy, the total organic carbon (TOC) removal efficiency was almost 70%, resulting in the observed release of SO42- anions. In addition, the concentration of dissolved oxygen decreased and the pH was lowered. Based on these results, irradiation with Co60 was found to be a useful tool to remedy wastewater containing sulfonated aromatic compounds.
Keywords: Advanced oxidation technology; Degradation; Irradiation; Mineralization; Sulfonated aromatic compounds.
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